1. Field of the Invention
The present invention relates to an ultrasonic welding structure obtained by oscillating a plurality of welding members with ultrasonic waves.
2. Description of the Related Art
As an earlier ultrasonic welding structure attained by oscillating objects with ultrasonic waves, there is known an ultrasonic welding structure of covered wires in Japanese Unexamined Patent Publication No. 9-320651 (U.S. Pat. No. 5,869,784).
In order to complete the above welding structure, a pair of covered wires are firstly arranged so as to intersect each other and thereafter, their resultant overlapping parts are interposed between an upper resin chip and a lower resin chip. While pressurizing the upper and lower chips from both sides thereof, the assembled chips interposing the covered wires therebetween are subjected to the ultrasonic oscillation in order to melt insulating covers of the wires at the intersection. After the covered wires have been electrically connected with each other at the intersection, the upper and lower resin chips are molten into one body to seal up the connection of the wires, thereby completing the connecting structure. Note, in order to interpose the covered wires stably, the lower resin chip is provided with recesses each having a waterproof groove, while the upper resin chip is provided with projections each having another waterproof groove, for respective engagement with the recesses. When assembling the upper resin chip to the lower resin chip for the ultrasonic oscillation, then both of waterproof grooves are integrated into one groove in which the molten cover of the wires is to be received, providing a waterproof sealing part of the connecting structure.
In the above-mentioned prior art, an ultrasonic horn is generally used for the ultrasonic waves for melting the covers of the wires and integrating the upper and lower resin chips. Meanwhile, in view of ensuring a welding fever, the ultrasonic oscillation is generally established in a manner that the oscillating direction of ultrasonic waves from the horn is perpendicularly to the objects' surfaces to be welded. Therefore, in the above connecting structure, a bottom face of each recess of the lower resin chip can be welded to a top surface of each projection of the upper resin tip owing to the adoption of the above relationship.
In the above-mentioned chips, however, opposing sidewalls defining each recess of the lower resin chip cannot be perfectly welded to opposing sidewalls defining each projection of the upper resin chip respectively since these sidewalls are all parallel with the oscillating direction of ultrasonic waves, which parallel relationship cannot provide a sufficient frictional welding fever between the upper and lower resin chips. Therefore, the resultant connecting structure is provided with perfect welded portions and imperfect welded portions in mix, which is far from the waterproof connecting structure. In other words, it means that, when ultrasonic-welding such objects having stepped portions as above, it is necessary to carry out the ultrasonic oscillating for several times in order to complete the waterproof structure.